U.S. Pat. No. 5,462,062 shows in FIGS. 5A-5E a bone marrow biopsy needle including an outer tube with an inwardly tapered distal end and an inner tube with a pair of opposed blades hinged to the inner tube at its distal end. The inner tube is slidable axially within the outer tube. At the distal end of the outer tube, the taper defines a dead space radially outward of the needle opening, and the blades have an open position in which they are contained within the dead space.
The outer tube is inserted into the bone being biopsied with the blades retracted into the dead space so as not to obstruct the entry of the biopsy core into the space within the outer and inner tubes. The outer tube is sharp to make entry into the bone as easy as possible. When the area which is to be biopsied has been entered, the inner tube is pressed axially in the distal direction. The blades engage the tapered end of the outer tube which folds them radially inward on their hinges, which simultaneously cuts off the biopsy core and retains it within the needle. A detent and blocking arrangement is provided for holding the inner and outer tubes in various positions relative to one another.
Although the above-described biopsy needle is effective and greatly improves the ease and security of the bone marrow biopsy process, it is desirable to make further improvements by reducing the number of moving parts, the manufacture of the biopsy needle, and the efficiency of its operation. More particularly, it is desirable to simplify the hinge arrangement, as well as the detent and blocking arrangement.